The disclosure of Japanese Patent Application No. 2000-107336 filed on Feb. 22, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety. The disclosure of U.S. Pat. No. 5,011,183 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to an airbag.
2. Description of the Related Art
Airbags are lately put to various uses. Examples of the uses are lifesaving jackets, life boats, mats, home elevators that utilize the expansion and shrinkage of airbags as a lift function, etc. In particular, airbags have been considered suitable for and have been used as airbags for protecting heads and chests of occupants in a vehicle by deploying at the time of a crash of the vehicle.
Airbags need to instantly inflate by taking air into a hollow portion. Particularly, where an airbag is used as a vehicular airbag, it is desirable to deploy the airbag rapidly at the time of a vehicle accident, for example, an accident in which the vehicle receives a side impact, or in which the vehicle rolls over. In particular, as head-protecting airbags, airbags for protecting side portions of occupants"" bodies from pillars or seat side portions of a vehicle are lately installed in an increasing number of vehicles. Japanese Laid-Open Patent Application No. 5-193430 discloses an art in which an airbag mounted in a portion above a side window of a motor vehicle is deployed downward to protect a side portion of an occupant""s head.
Many of these airbags employ integrally woven airbags, i.e., airbags that are woven together as one piece and thus do not require sewing or another joining method at an edge position where sides of the airbag meet. A very significant issue of integrally woven airbags is to secure a certain duration during which the airbag remains deployed. More specifically, there is a danger of insufficient strength of or air leakage from a boundary portion between a hollow portion and a single-cloth portion due to the opening of integrally woven caused by air pressure occurring in the air bag during the bag deployment. It is important to reduce this undesired phenomenon. In order to reduce air leakage during the deployment of an integrally woven airbag, there is a related art, for example, in which the aforementioned boundary portion is coated with a silicone resin or the like.
If the aforementioned boundary portion of an integrally woven airbag is provided with a firm texture, that is, a dense texture, yarns are naturally concentrated in the boundary portion, so that the boundary portion becomes protruded in comparison with other portions of the fabric, resulting in a projected-and-depressed or irregular surface. The presence of projections and depressions in a fabric may cause uneven coating particularly in the boundary portion during the resin coating of the fabric surface, thus causing undesired effects. Furthermore, a dense boundary portion degrades the fabric flexibility of the boundary portion, thereby resulting in deterioration in foldability. Foldability deterioration is undesirable because it is preferable that the installation space for an airbag be as small as possible.
Accordingly, it is an object of the invention to secure a low air permeability in an integrally woven airbag while flattening a boundary portion without forming a projected-and-depressed surface.
One mode of the invention is an integrally woven airbag characterized in that a texture of a hollow portion corresponds to 1 to 12 and A to K in each one of FIG. 1 and FIG. 2 illustrating a minimum component unit of a weave texture, and that a texture of a single-cloth portion corresponds to 1 to 12 and L, a and b in each one of FIG. 1 and FIG. 2, where a and b represent equal numbers of warp yarns, and assume an integer greater than one, and that a texture of a boundary portion is formed by 1 to 12 and L of the texture of the single-cloth portion indicated in each one of FIG. 1 and FIG. 2, and that a cover factor of the texture of the single-cloth portion is at least 4100.
In both FIG. 1 and FIG. 2, columns A to K form the hollow portion (a minimum repetition unit illustrated), and column L shows the texture of the boundary portion (a minimum repetition unit), and columns L, a and b show the texture of the single-cloth portion (a minimum repetition unit). Both a and b represent equal numbers of warp yarns, and assume an integer greater than one. In both FIG. 1 and FIG. 2, weft yarns are indicated by shading, and warp yarns are indicated by blanks. It should be appreciated that xe2x80x9cwarpxe2x80x9d and xe2x80x9cweftxe2x80x9d are interchangeable; e.g., if FIGS. 1 and 2 are rotated 90xc2x0, then the columns currently considered as warp yarns may be considered as weft yarns and vice versa.
In an integrally woven airbag in accordance with a first mode of the invention, the hollow portion may be woven in a hollow-weave. Thus, the weave texture has a specific pattern. The texture, or pattern, of the single-cloth portion has, for example, or pattern, that is generally termed 3/2 basket weave texture, 3/3 basket weave texture, or 3/4 basket weave texture. With regard to the retention of internal pressure of the airbag, a warp stitch length in the single-cloth portion texture that is greater than 3 weft yarns is expected to increase the opening of stitches caused by the internal pressure of the airbag. If the warp stitch length is shorter than 3 weft yarns, the production of the hollow-weave airbag becomes rather difficult. The number of warp yarns corresponding to the weft stitch length in the texture of the single-cloth portion can be 2 or greater, as can be understood from the aforementioned xe2x80x9c3/2 basket weave texture, 3/3 basket weave texture, or 3/4 basket weave texturexe2x80x9d. As for the texture of the single-cloth portion, the 3/3 basket weave is most preferable in view of the ease of production, taking into consideration the connection to the texture of the boundary portion described below. Furthermore, it is preferable that in the single-cloth portion texture, the texture of a boundary to the texture of the hollow portion part of be the basket weave texture of the single-cloth portion, but include only one yarn running parallel to the hollow portion. The term xe2x80x9cone yarnxe2x80x9d herein means that the number of yarns counted in a direction from the hollow portion toward the single-cloth portion is one. In addition to this condition, it is also preferable that the cover factor of the single-cloth portion is at least 4100. Correspondingly, the cover factor of the hollow portion is about one half of 4100. Furthermore, it has been found that the multiplier effect of the combination of the aforementioned weave structures and the value of cover factor of the single-cloth portion texture prevents air leakage from the boundary portion of the hollow weave, and reduces formation of a projected-and-depressed surface of the boundary portion of the fabric.
In the above-described mode, an outer surface of the hollow portion and an outer surface of the boundary portion may be coated with a layer of a rubber or a resin. Since this rubber or resin layer is provided on a smoothed boundary portion, uneven coating on the boundary portion is reduced. Therefore, the air leakage from the boundary portion occurring at the time of inflation and deployment of the airbag can be reduced. Furthermore, since the thus-coated airbag allows only a very small amount of air leakage, the airbag is suitable as a generally termed head-protecting airbag that is secured to a peripheral edge portion of a side window of a vehicle and that, when inflated, comes to a position between the window and an occupant.
An airbag of the invention may be subjected to scouring or thermosetting and, furthermore, to calendering on one or both side surfaces of a base cloth by a known method if necessary or desired, as long as features of the invention are not lost. In particular, for use as a vehicular airbag, it is preferable to reduce the air permeability by shrinking a base cloth by thermosetting or calendering to such an extent that the base cloth does not harden. In order to reduce the air permeability, it is particularly preferable to provide a coating layer of a rubber or resin, such as silicone rubber, polychloroprene rubber, urethane, etc. Since a calendered airbag has a smooth surface, the calendered airbag is particularly suitable for the coating of a thin-layer resin layer.
Furthermore, in a case where a different single yarn is mixed, as a rip stop, into a portion of the airbag, advantages of the invention can be achieved provided that the single yarn used substantially meets the requirements of the invention.